One electrophotographic image-forming device known in the art is a tandem-type color printer provided with a plurality of photosensitive drums corresponding to the plurality of colors (yellow, magenta, cyan, and black, for example) employed by the color printer. Some conventional tandem-type color printers are also provided with an endless conveying belt disposed in contact with all photosensitive drums, and a cleaning unit for cleaning the endless belt.
More specifically, one color laser printer that has been proposed includes a retaining member such as a process frame provided with four photosensitive drums corresponding to the four colors employed by the laser printer and, disposed within the process frame, a belt cleaner for cleaning a conveying belt, a waste toner collecting unit for collecting waste toner recovered by the belt cleaner, and conveying members (first and second screws and a lift) for conveying waste toner from the belt cleaner to the waste toner collecting unit.
Another image-forming device that has been proposed includes an image-forming unit supporting process cartridges corresponding to the colors employed by the image-forming device, and a belt unit having a sheet-conveying belt, the image-forming unit being provided with a waste toner collection box for collecting waste toner, and the belt unit provided with a belt cleaning device for cleaning the sheet-conveying belt, and a belt-waste-toner delivery tube for conveying waste toner collected by the belt cleaning device to the waste toner collection box.
With the color laser printer described above in the first example, the belt cleaner is separated from the conveying belt in order to remove the process frame from the main casing. However, when the belt cleaner is separated from the conveying belt, there is a chance that waste toner may drop from the belt cleaner.
Thus, efforts were made to prevent waste toner from dropping off the belt cleaning device by providing the belt unit with a belt cleaning device and a belt-waste-toner delivery tube, as in the image-forming device of the second example given above. However, in the image-forming device of the second example, the belt-waste-toner delivery tube projects into the main casing constituting the image-forming device, leading to the waste toner collection box. Consequently, the belt-waste-toner delivery tube may interfere with the image-forming unit when the image-forming unit is being mounted in the main casing.